This is a study of the association between low dose exposure to lead and the rates of Attention Deficit Disorder, School Dysfunction as measured by educational achievement scores, psychiatric status as measured by the CBCL and the DISC, and conduct disorder. The sample is 500 primary school students. Attentional function will be evaluated according to a four dimensional neuropsychological model, and the relationship of lead to any patterns of dysfunction evaluated. This is a retrospective cohort study in which the exposure variable is lead in bone as measured by in vivo X-ray fluorescence. The outcome measures are clinical scales of attentional function and behavior, psychometric IQ, and a battery of measures taken from the automated Neurobehavioral Evaluation System. Covariates to be controlled in the analysis include socioeconomic factors, experimental variables such as medical history and family variables. Odds ratios for ADD, school dysfunction and conduct disorder will be calculated from the data analysis. Analysis will initially be conducted by treating outcomes as discrete variables, stratifying for salient covariates and cross-tabulating against exposure. Additional analyses will be done using multivariate regression, with lead and attention as continuous variables. In addition, attentional function will be evaluated according to a neurobiological model comprising four dimensions. Correlations between patterns of function, lead exposure and school function will be measured. Lead poisoning has been shown to affect attention by a number of investigators. Lesser disturbances occur at lesser doses. The prevalence of low level lead exposure may be as high as 3-4 million American children. A reliable estimate of the lead-attributable risk for ADD will provide an important tool for public health officials, regulators and educators.